Method of making acetaldehyde.



,u eras lana unto.

HAROLD HIBBERT AND HAROLD ARTHUR MORTON, OF PIlIT'lSBURGH, PENNSYLVANIA, ASSIGNORS TO UNION CARBIDE COMPANY, OF NEW YORK, N. 'Y., A CORPORATION OF METHOD OF MAKING ACETALDEHYJDE.

VIRGINIA.

1,213,486. Specification of Letters Patent. No Drawing.

To all whom itmay concern:

Be it known that we, HAROLD HIBBERT, a

subject of the King of England, and HAROLD ARTHUR MORTON, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Methods of Making Acetaldehyde, of which the following is a specification.

In the manufacture of acetaldehyde from acetylene, it has been proposed heretofore to pass acetylene through a solution of a mercurv salt in sulfuric, phosphoric or benzenesulfonic acid, the mercury salt serving as a catalyzer in promoting the addition of water to the acetylene with the resulting formation of acetaldehyde. In'the practice of such processes, it is hightly desirable that the temperature of the bath should be suiticiently maintained so that the acetaldehyde may be continuously distilledoii'; but in operating at such temperatures it has heretofore been necessary, in order to avoid material production of crotonic aldehyde and other objectionable side products, to employ acid of relatively low concentration, for example below grams of SO per 1,000 gramsof Water.

We have found that it is practicable to employ acid ofmaterially higher concentration than the above, while operating at a temperature sufiiciently high for the continuous distillation of the acetaldehyde, and without appreciable production of crotonic aldehyde by adding to the solution a salt or salts of a relatively weak acid. By this term we mean to include the salt of any acid, the

ionization constant of which in a" six-percent. aqueous solution is less than that of a sulfuric acid solution of the same equivalent concentration; We except chromic acid, the

ionization constant of which is not known with certainty. The efi'ect of such additions is to reduce the concentration of thehydroder possible the employment, with its attendant advantages, of an acid solution havin a materially hi her concentration of S 4 than has hereto ore been practicable at the tem natures-required for the continuous distillation of-"the acetaldehyda-that is to say, atztemperfetures above Ci Such salts must of course jbe irreducible under'the operating conditions, in order that the de- App'Iication filed November 5, 1915. Serial No. 59,886.

Patented Jan. 23, 1911?.

sired efiect may be maintained. Sodium borate and sodium phosphate are'mentioned as illustrative examples of salts of weak acids suitable for use in accordance with this invention. I

While we have in the claims instanced sulfuric acid as a typical example of a strong acid, it is to be understood that other acids are to be regarded as equivalent thereto, namely, any acid capable of functioning in a manner similar to sulfuric acid, and the ionization constant of which is capable of being reduced to that corresponding to a six-per cent. SO solution by the addition of a salt of a relativelyweak acid, as defined above. i

An illustrative example .of the process is as-follows:To 8.4 liters of a sulfuric acid solution of 10.3 per cent. concentration are added 240 grams of mercuric oxid and 120 grams of borax. The solution 1s maintained at a temperature of 70 to 0., and acetylene is introduced at the rate of about 3.7 cubic feet per hour; The 'acetaldehyde is accomplishe at high efficiency (above per cent.) and the product is continuously distilled from'the solution and recovered b condensation. Such additions of salts o relatively weak acids may be advantageously made to solutions of strong acids other than sulfuric acid, as for instance to solutions of benzene-sulfonic acid, or of the acid sulfates of sodium or potassium: hence the invention is not limited to the employment of salts of Weak acids in conjunction with a sulfuric-acid bath.

A method of making acetaldehyde from acetylene in which the acetylene is introduced into a solution of an acid salt, with or without the addition of -a saltof a Weak acid, is disclosed and claimed in a copending application Serial No. 59,837, filed November 5, 1915.

We claim I.

1. The method of making acetaldehyde, whichconsists in introducing acetylene into a solution of sulfuric acid, said solution containing also a salt of mercury and a salt of a relatively weak acid, said salt being irremi ducible under theoperating conditions.

2. The method of making acetaldehyde, which consists in introducing acetylene into a solution-of sulfuric acid, said solution contaming also a salt of mercury and a salt of a relatively weak acid, said-salt being irre- 4; The method of making acetaldehyde, which consists in introducing acetylene 1nto 10 a solution of sulfuric acid, said solution con-o taining also a salt of mercury and a borate,

and simultaneously distilling acetaldehyde from the. solution.

In testimony whereof, We aflix our signatures in resence of two Witnesses.

' AROLD HIBBERT, HAROLD ARTHUR MORTON. Witnesses:

. S. G. PERRING,

Gno. B. NICKEL. 

